Absorbent articles such as diapers, adult incontinence garments, feminine care products, child training pants, pull-ups, bandages, gloves and similar products that directly contact skin are well known. A disposable absorbent article is typically composed of a top layer that is adjacent to a user's body and a back layer that faces the clothing of the user. An absorbent material is located between the top layer and the bottom layer. The top layer permits a liquid from the user to move through the top layer toward the back layer. The back layer does not allow liquid to be transferred from the inside of the absorbent article onto the user's clothing. The absorbent material absorbs the liquid and keeps the skin dry.
During normal operation after a fluid is discharged from a user, the fluid will flow through the top layer and be absorbed by the absorbent material. The absorbent material is designed to absorb, redistribute, and store the fluid until the absorbent article is discarded. In some instances, however, fluid may return from the absorbent material to once again contact the user's skin. Fluid return can occur, for instance, if the absorbent material cannot sufficiently absorb the fluid due to the composition of the absorbent material. Unabsorbed liquid undesirably results in over-hydration of the contacted skin and in turn, increases a chance of skin irritation to the user. In addition to being an irritant, excessive moisture on the user's skin can cause, among other things, the growth of microorganisms that can lead to the onset of rashes or infection.
Various tests exist for measuring performance and suitability of absorbent materials to prevent the foregoing problems. Known tests include capacitance, capacitive reactance, conductance, electrical impedance, and/or evaporative or Trans-Epidermal Water Loss (TEWL) evaluations. Typically, these tests measure fluid absorbency, fluid leakage, and other criteria of the materials for use in absorbent articles.
By way of example, the Adult Forearm Test or “armband” test is conventionally used to evaluate the effectiveness of disposable diapers to keep the skin dry. In the armband test, changes in skin surface hydration are measured by evaporimetry or TEWL evaluation. To maintain a healthy and moisture-balanced skin, the TEWL readings between un-diapered and diapered skin should not differ significantly. One variation of the armband test uses pre-loaded patches from diapers placed on an adult volar forearm, and differences in skin surface hydration between cloth diapers and disposable paper diapers have been noted.
Another armband test uses an intact diaper wrapped around the forearm. Physiological saline is injected into the diaper at a rate and volume that represent normal urination by a child. Post-occlusion measurements are made after one hour, and measurements of skin hydration are made by computerized evaporimetry or by electrical conductance.
The above and other common tests have been used extensively for evaluating skin hydration of covered or diapered skin. It would be advantageous to have a bench top instrument that produces results similar to the TEWL test to reduce for instance high variability found in conventional tests.